What about the Stockholm arhipelago?

I love a good, calm boat ride around the archipelago and I frequently say that May is the best time to visit Sweden. Discovering small islands this time of a year has a special feeling to it. It’s still quite calm, because the summer season hasn’t started yet. The weather is amazing and it's a great oportunity to make hay while the sun shines, as some might say. Unlike the real summer that tends to be wet and cloudy, this time of a year will make you want to swim in the cold Swedish wather. I wouldn't recommend such activity, but thinking about it could fill up your time on the way to a special island...one of thirty thousand that you can choose from. 

Here is a view of 0.01% of all islands that surround Stockholm:

Grinda

Vaxholm

Birka